One of the problems related to data transfer through a common data communication channel, like the Internet, is the exposure of transferred data to hostile objects (“hackers”). In fact, everyone who has access to the Internet may be considered a threat. Consequently, as the number of Internet users increase, so too does the interest in protecting transferred data. As such, the security of data transferred through the Internet has become an issue of interest.
There are two major ways of protecting transferred data: ciphering and integrity validation, i.e. testing that data has not been tampered by an unauthorized object. Integrity validation is normally used when the authenticity of the data is being protected, while ciphering is normally used when the data itself is being protected.
In addition to the traditional Web data that passes through the Internet, such as Web pages and email messages, the Internet has also become a common channel for passing software packages and software updates. A software package usually comprises a collection of files, each of which may be protected by encryption or by digital signatures. The methods currently used in the art may prevent individual files from being tampered with, but they do not refer to protecting a collection of files, or the properties associated with that collection, from tampering, which results with security problems. For example, a software component may be replaced by an earlier version of the same component, in order to bypass restrictions on the use of the whole software package.
It is therefore an object of the present invention to provide a method for indicating the integrity of a collection of digital objects (such as files, email messages, etc.)
It is a further object of the present invention to provide a method for indicating the integrity of a collection of digital objects, in which the collection itself and the information about the relationships between the objects, is protected along with the digital objects themselves.
Other objects and advantages of the invention will become apparent as the description proceeds.